It is not uncommon for a cow or a sheep to push her uterus out of the birth canal when calving. When this occurs it is referred to as an "uterine prolapse". The method of treatment is for a veterinarian to manually reposition the uterus, and then place pins through the vulva to create an obstruction which prevents the uterus from being pushed out again. This treatment is effective only if the animal stops "pushing". In most cases, however, the uterus is pushed against the pins, the cervix does not contract to its normal size and the animal continues to push. The result is a painful condition that obstructs the normal bodily functions of the animal, leading to a gradual deterioration in the health of the animal and eventually death. Even if the treatment is effective, the piercing of the skin with pins can lead to a secondary problem of infection.